AUSTIN, Texas (AP) – Police shut down 10 blocks of businesses in the heart of downtown Austin early Monday after dozens of birds were found dead.

Emergency workers donned yellow hazardous-material suits, and dozens of fire trucks and ambulances were parked nearby, as they began testing for any sort of environmental contaminant or gas or chlorine leaks that might have cause the bird deaths.

There were no reports of any humans harmed, but a 10-block stretch of the main north-south route through downtown, several side streets and all buildings in the area were blocked off and expected to remain off-limits until about noon, said police spokeswoman Toni Chovanetz.

“There is no credible intelligence to suggest an imminent threat to the homeland or the Austin at this time,” said Department of Homeland Security spokesman Russ Knocke.

Homeland Security, the Department of Health and Human Services and state authorities are monitoring the situation, he said.

The bird carcasses were found overnight along Congress Avenue between Sixth and Eighth streets.

The street closure Monday morning stretched from the front of the state Capitol to a section of the Colorado River known as Town Lake. The Capitol opened on schedule Monday, the day before the legislative session was to begin.

On the East Coast, New York City also had a scare Monday morning when a mysterious gas odor moved across Manhattan. It wasn’t immediately clear what had caused the odor, and it dissipated fairly quickly. No injuries or damage to wildlife was immediately reported.