SAN DIEGO -- Motorists and pedestrians entering the United States from Mexico Monday at local border crossings continued to face long lines because of heightened security.

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The stage 1 security alert -- the highest level of security used by the Immigration and Naturalization Service -- was ordered after last Tuesday's terrorist attacks.

According to 10News, motorists can expect to wait between two and four hours in lines.

"The purpose of this is the protection of the public," an INS dispatcher said. "We're just reminding everybody to be patient. There is a high-security alert in effect."

Pedestrians waited up to two hours to cross the border Sunday.

The total number of people seeking to cross the border was down in the aftermath of the attacks on the East Coast, with only about 90,000 people crossing at San Ysidro on Thursday, about 40,000 fewer than cross on a typical weekday, the dispatcher said.

"It does appear that the number of people and vehicles is somewhat reduced," the dispatcher said.

About 10 miles to the east, the wait for motorists Sunday at the Otay Mesa point of entry was about an hour. Normally, the wait is only 45 minutes. Pedestrians waited five to 10 minutes to cross at Otay, the dispatcher said. Usually there's no wait, she said.

The dispatcher said that the INS has not received any information on when the stage 1 alert would be canceled or reduced.

Two bomb threats, one last Tuesday night and the other Thursday night, forced the closure of the San Ysidro checkpoint for two hours each time. No explosives were found in either case.