A bomb was left in a duffel bag in the parking lot of a clinic where abortions are performed, but a bomb squad safely detonated it.
An employee found the package Wednesday in the parking lot of the Austin Women's Health Center, authorities said. The immediate area, including nearby Interstate 35, was evacuated briefly.
The device "was configured in such a way to cause serious bodily injury or death," said David Carter, assistant chief of the Austin Police Department.
Tests later confirmed that the package was explosive. The regional Joint Terrorism Task Force, led by the FBI and including Austin police, is investigating.
Authorities have asked area abortion providers to be vigilant in coming days, Carter said.
A U.S. Supreme Court ruling last week banned a type of late-term abortion.
"We know that when abortion is in the news, we also see clinics targeted for increased violence and disruption," said Vicki Saporta, president of the National Abortion Federation. The group put out a memo to abortion providers around the country, urging them to be alert.