An Amtrak train from Washington's Union Station to Boston was delayed yesterday morning for nearly two hours in Newark, N.J., after a passenger discovered a suspicious note attached to a mirror in the restroom of the cafe car.

Amtrak spokesman Dan Stessel said Train 170, carrying about 450 passengers, was detained for 90 minutes in Newark's Penn Station after a passenger discovered the "threatening" note. New Jersey transit and Amtrak police were waiting when the train arrived. Bomb-sniffing dogs were brought on board as officers checked passengers' identification. After determining there was no immediate threat, authorities allowed the train to continue.

The note was handed over to the Federal Bureau of Investigation. Its details were not released. Stessel said the threat was not specifically against the passengers of the train but was of a "general threatening nature."

It was the second time this month that an Amtrak train was delayed because of a perceived security threat. A train from Miami to New York was stopped at Washington's Union Station for more than an hour on July 3. Officials stopped the train after graffiti threatening Washington was discovered in the men's bathroom at the Amtrak station in Orlando.

Stessel said Amtrak receives about one or two threats a week that require security officials to delay a train.

Rail authorities have been on higher alert since train bombings in Madrid killed almost 200 people March 11. Security precautions also have been increased for the Democratic National Convention in Boston next week and the Republican convention in New York in August.

"We are nearing the convention season. Everyone is on a heightened state of alert," Stessel said.

Spurred by the Madrid bombings, the Transportation Security Administration has been testing its airport security procedures on Amtrak trains. Last month the security agency conducted a three-week test of luggage screening at Washington's Union Station. The TSA also has conducted a test program to search carry-on items and screen passengers at Amtrak's New Carrollton stop. Passengers there walked through an explosives detector, and their bags were X-rayed.

Earlier this week, the TSA began testing a program to screen passengers and bags on a moving train. The project, which involves screening passengers after they board, is taking place on Connecticut's Shoreline East commuter line, Stessel said.