SAN JOSE -- Authorities scoured a building at eBay's PayPal division Wednesday for clues about a Halloween night explosion that shattered a window and forced the evacuation of dozens of employees.

PayPal spokeswoman Amanda Pires said the company had not received any threats but declined to comment further on the investigation of the blast Tuesday that hit the first floor of the company's network operations center.

"We believe this is an isolated incident," she said. "We're working closely with local authorities. We have everything under control."

Business was not disrupted, but the complex was closed Wednesday and cordoned off by police tape. About 1,900 eBay and PayPal employees who work in buildings on the campus where the explosion occurred were asked to work from home or at another eBay campus in San Jose, Pires said.

The blast occurred near an outdoor corridor popular for employee breaks and was not visible from the street. A 6-by-7-foot window was shattered, but there was no other damage.

Dozens of employees were evacuated following the explosion, but no injuries were reported, said Sgt. Nick Muyo.

No explosive device was found, but investigators determined the blast was deliberately set, he said. There were no suspects.

"It's definitely not an accident," he said. "Everything else there is accounted for. This was not any kind of accident or malfunction."

Investigators from the San Jose police and fire departments, the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives were investigating the blast. The investigation was being taken over by San Jose police.

PayPal, which provides a platform for online payments, is a lucrative division of eBay, generating some $350 million in revenue for the online auction company in the latest quarter.