A steam pipe exploded at Fifth Avenue and 21st Street in New York City at about 6:40 a.m. ET on Thursday.

The incident prompted the evacuation of 28 buildings and warnings of possible asbestos.

Authorities are asking people to stay away from the affected area.

Five minor injuries have been reported, according to the New York City Fire Department.

A steam pipe explosion in New York City's Flatiron District on Thursday morning sent steam spewing high above buildings and created a craterlike hole on Fifth Avenue.

The explosion, which occurred at about 6:40 a.m. ET at Fifth Avenue and 21st Street, prompted evacuations of at least 28 buildings, the New York City Fire Department said on Twitter, adding that five minor injuries had been reported.

The incident also sparked concerns about asbestos.

"Environmental testing is being conducted to determine whether asbestos or other contaminants are present, but as a precaution anyone in the vicinity of the rupture who was covered in material is advised to bag their clothing and shower," Con Edison said in a statement on Twitter at about 9 a.m.

Emergency responders near where the explosion happened. Brendan McDermid/Reuters

The energy company warned people to stay away from the area as a safety precaution. Fifth Avenue from 20th to 23rd streets was also shut down.

The FDNY said that while it was still waiting on lab results to see whether asbestos was present, it was acting as if they would be positive.

"We're operating with an abundance of caution since this steam main was installed in 1932, so there is possibly a presence of asbestos," FDNY Commissioner Daniel A. Nigro said in a statement on Facebook. "Samples have been taken and we're awaiting the lab results. We are operating as though those samples will come back positive."

Those who feel they were affected should report to one of two decontamination sites set up on Fifth Avenue — at 19th Street and at 22nd Street — where they can be evaluated, Nigro said.

Those who witnessed the explosion quickly posted footage on Twitter.