HOULTON – U.S. Customs and Immigration inspectors along the U.S.-Canadian border were placed on a heightened state of alert shortly before noon Tuesday in the wake of the terrorist attacks on buildings in New York City and Washington, D.C.

Bert Magnus, U.S. Customs area port director at Houlton, said doors at the Customs and Immigration building in Houlton not normally manned were secured, and staffing at small ports of entry where there is usually only one inspector was doubled.

“That’s a safety issue,” said Magnus, noting that the last time border crossings were put on heightened alert was after a woman with ties to terrorists was apprehended at a border crossing in upstate Vermont just over a year ago.

Border inspectors on Tuesday also were under orders to check the identifications of all people entering the United States and to inspect all vehicles.

“Inspectors will take a little extra care in checking who they are and what they’re doing,” Magnus said about people entering the United States.

At the Madawaska port of entry, the 13th busiest port along the U.S.-Canadian border, cars and trucks were lined up at about 1 p.m. halfway across the bridge to Edmundston, New Brunswick.

Instead of the usual one officer, there were four handling traffic in two lanes. Two of them were checking cars, and two others assisted traffic, telling people about searches.

One man, who was opening his door to exit his car, was quickly told to remain inside the car until he was asked to come out.

Nothing was left outside of the realm of the searches. They involved drivers opening trunks, glove compartments and other compartments of vehicles. Officers lifted coverings in trunk floors and looked into bags and containers in the vehicles.

All the compartments in an 18-wheel tractor-trailer were checked individually, including the large trailer box.

People with campers in tow were asked to open them so that inspectors could check closets, storage areas and luggage.

“We can’t comment on security measures,” Lloyd Woods, Madawaska Immigration supervisor, said. “The border is open.”

Though the increased security delayed people a little longer at the border crossings, people seemed to understand.

Robert Y. LaFrance and his wife, Armande, of Edmonston, New Brunswick, were driving to Boston to meet friends before they continued on for a week of vacation in New York City. When they heard about the attacks, they canceled their trip and decided to visit family in Moncton, New Brunswick, instead.

After they were checked at Houlton, they turned around and headed back to Canada.

“We’re sad that they’re hitting your country,” said Robert LaFrance, a customs inspector in Canada, noting that the impact of the terrorist attacks was bound to spill over into Canada. “It’s a shame we have to deal with these people; with the hatred.”

“We like this country,” added Armande LaFrance, who said the trip to New York City was to have been the realization of a childhood dream for her.

Tim Donnell, area port director at Calais, said the situation there Tuesday was much like that at other ports along the U.S.-Canadian border, but otherwise, nothing unusual had happened.