Four East Bay police departments received a scare Friday when envelopes filled with white powder showed up in their mail, sparking investigations from hazardous materials crews and the FBI.

The substance in three of the envelopes -- those delivered to police in Hayward, San Leandro and Berkeley -- was not hazardous, officials said. A fourth envelope delivered to the Union City Police Department was given over to U.S. Postal Service and FBI for more investigation, police Cmdr. Kelly Musgrave said. Test results weren't immediately available.

No other police departments reported receiving similar envelopes, but agencies around the Bay Area were alerted to it, Alameda County fire spokeswoman Aisha Knowles said. The substance delivered to San Leandro was baking flour, Lt. Greg Lemmon said, but authorities did not identify the substance found at the other stations.

Authorities also did not say whether they believe the deliveries are connected.

The first discovery was made around 10 a.m. at the Hayward Police Department, when a records clerk sorting through the mail the discovered white powder had leaked out of an envelope station at the station, Hayward fire Capt. Thor Poulsen said.

Police placed the envelope, which had no return address, in an interview room and called fire crews from Hayward and Alameda County. They ordered the first floor evacuated while police personnel remained in the building's second story.

Around 11:30

The Hayward station's first floor reopened around 1:30 p.m., police said.

The powder-filled envelope in Berkeley was uncovered by a staff member at the building that houses the police and fire administration on Martin Luther King Jr. Way about 2:17 p.m., police said. Berkeley police immediately called the Berkeley Fire Department, which used a chemical detector to determine the substance wasn't toxic.

"We were able to use a device that could immediately identify what kind of substance we were dealing with, so we were able to know right away that it was nonhazardous," Berkeley Deputy Fire Chief Gil Dong said.

The first floor of the building was evacuated during the investigation. The heating and ventilation systems were closed down, Dong said, and the envelope remained in the room it was discovered behind closed doors.

Union City police officials were alerted by Alameda County Fire officials to be on the lookout for such an envelope, Musgrave said, and they found it around 2 p.m.

"If we hadn't got the tip, we would've been doing this on Monday," Musgrave said. Union City closes most of its offices on Friday, and mail is not normally distributed.

This time, Musgrave went looking for the envelope and found it in the mailroom. He said he immediately called the hazardous materials team, and put the envelope in a room separate from any employees.

No injuries were reported in any of the incidents and the people who handled the envelopes have not shown any signs of illness, authorities said.

Next, the police agencies will conduct a joint criminal investigation to find out who mailed the substances to them.