OAKLAND -- Oakland Police confirmed Saturday it was the fifth agency in the Bay Area to receive an envelope filled with white powder in the mail sparking investigations from hazardous materials crews and the FBI.

The unidentified substance, determined not to be hazardous, was discovered sometime early Friday evening, Oakland Police said.

The substance in three other envelopes delivered Friday to police in Hayward, San Leandro and Berkeley was also not hazardous, officials said. A fourth envelope delivered Friday to the Union City Police Department was given over to the U.S. Postal Service and the FBI for more investigation, police Cmdr. Kelly Musgrave said.

Test results weren't available Saturday.

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

Around 11:30 a.m., the Alameda County hazardous materials team tested the substance, determined it was nonlethal, then sealed any items that came into contact with the substance in plastic bags, Poulsen said.

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.

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.

At least four of the police agencies plan to conduct a joint criminal investigation to find out who mailed the substances to them.

On Saturday Oakland Police had not announced its plans.