UPDATE: Two men seriously injured following explosion at the DPW Lincoln Avenue Garage

The Milwaukee Police Department confirms that two men were seriously injured in an explosion this afternoon.

The explosion happened shortly before 1 p.m. at the DPW Lincoln Avenue Garage near 39th and Lincoln.

The men were transported to a local hospital.

A van parked at the compressed natural gas station appeared to have a hole in the roof.

Tow lot cashier Alyssa Schnoebelen says you could feel the force as well as hear the blast.

"Just a big boom," she said. "It sounded like something hit the building. We thought somebody crashed at first. I was like Holy Crap what just happened?"

Worker from down a block say they felt their buildings shake. 

Some scrambled to the scene to help.

"I came out and saw a guy crawling into the bushes," said nearby worker David Lau. "That's when I ran back and called 911."

Investigators were seen pouring over the wreckage hours after the fire crews had cleared the scene.

"I thought it was a sonic boom," said Karen Volz who works nearby. "Everybody stood up. Looked around. But it was clear it was a distance away. We're a little over a block away and our building shook. It was quick. I was just thinking what could that possibly be?"

The Milwaukee Fire Department confirms that there is a 300-yard evacuation zone at the DPW lot where the explosion happened. According to the fire department, it's because of two compressed natural gas tanks. There were 3 on a truck and one blew up and now they are trying to figure out how to relieve pressure for the other 2.

As of yet, we don't have a cause.