CITRUS HEIGHTS, Calif. -- To help make shipping easier during the holiday season, the U.S. Postal Service has set up automated centers all over the country. But with all the security threats, a former top government inspector says the Postal Service is backpedaling on security in order to make a profit.

There are 40 automated postal machines in the Sacramento region, from Redding to Fresno. The Postal Service plans to have 2,500 nationwide by the end of the year. They allow anyone to mail a package day or night.

During the process, the customer weighs the package and uses a debit or credit card to pay for the postage. The machine prints a stamp for the exact amount, and the customer puts the package in a drum.

"As long as it will fit in (the) bin, they can drop it in here, up to 70 pounds," said U.S. Postal Service spokesman Ralph Petty.

But it's what happens or doesn't happen next that is raising serious security concerns. According to the Transportation Security Administration, only a small percentage of mail is randomly screened for explosives and hazardous materials before being shipped. And many packages end up on cargo planes.

"These automated postal centers are definitely increasing the risk to aviation and to Americans," said former Inspector General Mary Schiavo.

Schiavo has ruffled some feathers, pointing out security lapses in the aviation system.

"We seem to have, as a nation, a very short collective memory," Schiavo said. "We've all but forgotten about the 'Unabomber.' We've forgotten about the letter bombs that came from the Middle East. We've forgotten about the poisons that were mailed after (Sept. 11, 2001)."

For a while after Sept. 11, 2001, the Transportation Security Administration had a program that used dogs to check air cargo for explosives. But they only did it at a dozen airports, and it was a temporary pilot program. The TSA can't say when it might be revived.

From 1978 to 1995, "Unabomber" Ted Kaczynski dropped off or mailed numerous bombs that injured 23 people and killed three, according to prosecutors. Two victims died in Sacramento.

In the wake of those attacks, warning signs went up at mailboxes. Since then, people are no longer allowed to mail packages that weigh more than 16 ounces using regular postage stamps. The idea was to make customers come face to face with a clerk who might notice something suspicious.

Yet critics say the automated postal centers let people bypass that precaution and put packages in the system without anybody looking.

Todd Curtis is an aviation safety analyst who runs a Web site called Airsafe.com.

"One level of security, one level of investigation, one level of analysis is not going to be there," Curtis said.

But the Postal Service says there are safeguards and deterrents. The automated machines have cameras that can take pictures of customers, who also have to use a credit or debit card.

"We screen the packages when we take them out. We don't send anything on commercial airlines any more that are over 16 ounces," Petty said.

But it took less than 16 ounces of explosives to bring down Pan Am flight 103 over Lockerbie, Scotland. And even if a bomb didn't get on the plane, it's still in the U.S. postal system and could go anywhere.

The U.S. Postal Service insists it is committed to the sanctity of mail safety, and the automated postal centers create no greater risk than dropping off a package with a clerk.

"We're on the lookout all the time. We've trained our clerks to look for things that are suspicious all the time. We would hope that everything would be on the up-and-up, but you always have to be on alert," Petty said.

"This is one of those situations where it's business as usual, and the value of mail contracts and the carrying of the mail is taking precedence over security," Schiavo said.