NEW YORK (CBSNewYork) – The small explosion inside a garbage truck on the Upper West Side Friday morning was caused by an improperly disposed of oxygen cylinder, officials said.

An oxygen cylinder exploded in the back of a Santitation truck on Feb. 8, 2018. (credit: DSNY)

It happened shortly after 7 a.m. Friday near 90th Street and Amsterdam Avenue.

The NYPD hazmat team responded and raked through the truck’s contents. The FDNY also inspected the vehicle, called a “hopper.”

“We did not find any corrosives or any materials in the back of the hopper or any type of devices,” FDNY Chief Nicholas Corrado said.

Nearby buildings and businesses were not evacuated.

“We have had these in the past. We did not feel as though there was any real danger to any of the residents,” said Corrado.

Two sanitation workers suffered minor injuries after being jolted by the blast.

Department of Sanitation Deputy Chief Ed Grayson said residents need to pay attention to what you can and cannot throw out.

“It’s like high school science – a certain mix of the right chemicals can cause anything to be combustible,” he said.

“Small oxygen tanks and other materials like liquid solvents, automotive materials, flammables and electronics, can seriously harm sanitation workers and landfill employees and contaminate our waterways if they are not safely disposed. They should never be placed with regular garbage collection,” the Sanitation Department said in a statement.

For a full list of items requiring safe disposal, click here. For a list of special waste drop-off sites, click here.

Those who live in the neighborhood were a little uneasy.

“It’s very disturbing. You wonder what kind of explosion, was something intentionally put in there?” said Phil Rosenthal.

“My two kids come here to preschool, so that’s why I got tears in my eyes. I was like, are we OK to come to school?” Tammy Sikorjak said.

The sanitation workers are both expected to be OK. The truck was taken back to DSNY headquarters for further inspection.