Everyone was startled when they heard this, and hurriedly took the flashlight in their hands and began to shine, only then did they realize that they didn't know when, the ground had begun to be filled with fog.

Coupled with the fact that the only lighting equipment inside came from their flashlights, everyone was either busy observing the situation around them or studying the remaining equipment, all ignoring the danger under their feet.

"Everyone cover their mouths and noses!Retreat to the passage in an orderly manner!" Long Xiaoyun covered his mouth and nose and shouted to the rioting crowd.

At this point, the scholars were already flustered, and pushing each other in the dark would only make the situation more dangerous.

Those well-trained bodyguards and special forces naturally took charge of protecting the safety of their employers, and began to guide their teams to retreat quickly towards the passage.

Bang!

A gunshot suddenly rang out in the darkness, and no one knew where the gun was fired or who fired it, and the scene suddenly became chaotic.

"Dr. Shi!"

An exclamation suddenly came from one of the ranks, and an old man touched his chest in disbelief, which had already been stained with blood.

He pulled the student next to him, and his body slipped off the student weakly, blood continued to spread on the ground, and Dr. Shi's body went limp, and he had already lost his life.

"Ahh

"I'm going home!"

"Run, someone's going to kill us!"

Where had these students seen such a situation, they suddenly lost their opinions, left their teachers, and exclaimed that they were about to rush to the passage.

But the passage is so wide, if a person accidentally falls down, inhales the poison gas directly, and then a stampede occurs, it will undoubtedly increase the difficulty of escape.

Yao San simply didn't do anything, took out his pistol, and fired two shots into the air!

"Return to your own team one by one!Retreat in order!" Yao San shouted angrily.

As soon as Yao San shot like this, he really frightened these students who had never seen the world, and returned to his team crying one by one, and continued to evacuate the scene under the escort of their respective bodyguards.

Yao Er was on the other side, secretly observing who fired the shot.

At this moment, Long Xiaoyun's watch communicator rang.

"Dragon... School... Captain. In this sealed space, the signal reception is very weak, and Li Cheng's voice comes intermittently from the watch.

"Hey, hey, newcomer, we're in danger!

Long Xiaoyun shouted towards his watch, but there was a murmur of disconnection.

"Still can't get connected?" Tian Guo looked at Li Cheng anxiously.

Li Cheng frowned tightly and nodded slightly, maybe his position was too far away from Long Xiaoyun, and the signal was very unstable.

After they blasted open the rock wall, a large hole appeared, which was obviously made of man-made structures, and a passage was poured concrete, but this passage was vertically downward, and the surface was smooth and they could not go directly down.

Shining down with a flashlight, he couldn't see the bottom at all, Li Cheng simply picked up a small stone and let it fall naturally.

Both of them listened attentively, but Tian Guo's brows were slightly furrowed, because she didn't hear the sound of the stone falling to the ground at all.

Li Cheng's hearing was extremely keen, and he silently counted the time when the stone fell, until an inaudible sound came from the bottom.

"The landing time is more than three seconds, the speed of sound propagation in the air is 340 meters per second, and the gravitational acceleration, according to the formula of free fall, is almost between 30 and 40 meters. ”

Li Cheng calculated the approximate depth of the passage, and Tian Guo, who had not heard anything next to him, was stunned by his series of data and conclusions, and there was a look of adoration in his eyes.

There are no specific requirements, generally speaking, the length of the climbing rope is a little more than 20 meters, so there is still some distance from the ground.

Tian Guo gritted his teeth and said, "I'm relatively light, why don't we pick up the rope and let me go down to investigate?"

"No, I don't know what the situation is below, it's too dangerous to go down rashly, the end of this passage may be the place where Long Xiaoyun and the others go, let's contact her first!"

On Long Xiaoyun's side, the team began to enter the passage one by one, and everyone thought that they were about to escape.

Suddenly, there was another boom, and the space began to tremble, and everyone could hear a heavy muffled sound at the other end of the passage, and the tremors and loud noises disappeared with it.

At this time, the people at the front began to become agitated, and desperate cries were constantly heard.

Long Xiaoyun secretly screamed in his heart, and rushed to the front with Yao San.

Seeing that the passage that originally led to the outside was blocked by a black stone slab, Yao San angrily raised his ** and smashed it down towards the stone slab.

But what was fed back to her was a crisp hitting sound, and there was no empty echo, which showed that the thickness of this stone slab was beyond their imagination.

The metal on the gun scraped through the slate and a string of sparks burst out, which showed the hardness of the slate and it was not something she could smash open.

If it was a little thinner or not so hard, Yao San would still be able to use fire to force it and smash the slate, but the current situation completely killed her idea.

Yao San looked back at Long Xiaoyun and said softly: "Colonel Long, now I'm afraid that only by using ** can it be possible to blow up this stone slab." ”

But Long Xiaoyun didn't answer her immediately, and Yao San didn't dare to use ** rashly.

Because they all know that if they use ** in such a small place, if the mountain is blown up and causes the mountain to collapse, then they will really have to be buried here.

Obviously, I have sent people over to survey the terrain several times before, but there has been no situation, but today so many people have been dispatched, and it has suddenly become dangerous, could it be that there are other forces behind them, secretly monitoring them!

The poisonous gas underneath began to slowly spread upwards, and Yao San took out a portable oxygen supply from his backpack.

Normally, if they are alone, the oxygen supply can provide oxygen for about 10 hours, but there are 17 people on site, and I don't know how long it can last!

Seeing the poisonous gas surging towards this side, the people who had not yet entered the passage began to squeeze in hard.

Seeing that the situation was getting more and more dangerous, Yao San frowned and said: "Colonel Long, both horizontal and vertical are dead, just use **! If it continues like this, I'm afraid it will affect more people!"

Bang!

Before Long Xiaoyun could speak, another gunshot rang out, and then the crowd began to riot again, and a student fell in a pool of blood.

"There's an enemy attack!"

Yao Er finally determined that the gunfire did not originate from his own position, but in the dark, but the other party may have installed a flame suppressor, and the flame was extinguished, and he couldn't tell where it came from.

Bang!

This bullet was fired directly at Yao Er, who gave a warning!