An explosive device blew out a thick, plate-glass window Tuesday evening at the Silicon Valley headquarters of PayPal, Reuters reports.

No injuries resulted when what local fire officials said was an explosive device shattered a 6-foot-square window on the ground floor of the four-story building in San Jose, California. The explosion occurred outside a building exit.

Investigators were still trying to determine the nature of the device. "Whatever it was, it disintegrated," San Jose Fire Department Capt. Jose Guerrero said. "Whatever caused this was pretty strong."

About 45 employees were working in the PayPal offices when the explosion occurred at 7:24 p.m., eBay spokesman Hani Durzy said. Most employees had left the building early ahead of the Halloween holiday celebrations, he said.

"We have no reports concerning threats," Durzy said. "We are still investigating and we are working with local and federal authorities."

The PayPal offices, where 1,900 employees work, were closed Wednesday while police conducted an investigation. They are expected to reopen on Thursday.

No eBay or PayPal online services were interrupted by the blast, the spokesman said.