AUSTIN, Texas (AP) -- Police shut down 10 blocks of businesses in the heart of downtown early Monday after dozens of birds were found dead in the streets, but officials said preliminary tests showed no dangerous chemicals in the air.

As many as 60 dead pigeons, sparrows and grackles were found overnight along Congress Avenue, a main route through downtown. No human injuries or illnesses were reported.

"We do not feel there is a threat to the public health," said Adolfo Valadez, the medical director for Austin and Travis County Health and Human Services. He said preliminary air-quality tests showed no dangerous chemicals and the area should reopen around noon.

U.S. Department of Homeland Security spokesman Russ Knocke said officials had no credible information to suggest any imminent threat to the city.

On Congress Avenue, just outside the state Capitol, emergency workers donned yellow hazardous-material suits Monday morning, and dozens of fire trucks and ambulances were parked nearby.

Workers were testing for any sort of environmental contaminant or gas or chlorine leaks that might have cause the bird deaths, said police spokeswoman Toni Chovanetz. At least one bird carcass was being tested locally for other possible causes, and other carcasses were shipped to the Centers for Disease Control and Prevention and Texas A&M University.

Valadez said the tests on the dead birds would likely take several days and look for signs of poisoning or viral infections, though he said officials do not think bird flu is involved.

A 10-block stretch of Congress Avenue, several side streets and all buildings in the area were shut down and declared off-limits as a precaution, Chovanetz said.

The street closure stretched from just outside the 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.

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