A similar letter was sent to Senate offices. The suspension of mail would last indefinitely, said Lt. Dan Nichols, spokesman for the U.S. Capitol Police. He said the material was sent to an Army base for definitive testing
Staffers said the mail delays would not affect members' business. Congressional staffers who handle mail attended a security briefing on what to look for when opening letters and packages, Neugebauer said.
A conference call for workers in district offices was scheduled for later Monday. The House was not in session Monday, meaning most of the area's congressional representatives were out of town. Staff members were at work.
"We're taking the situation very seriously," said Mike Harrison, press secretary for Rep. Duncan Hunter, R-Alpine.
"It just goes to show you that we have to be very prepared." Aaron Hunter, spokesman for Rep. Susan Davis, D-San Diego, said the office had been vigilant even before Monday's occurrence, checking mail with excess postage, protruding wires or misspelled words.
"We've been extra cautious with the mail that has come in," he said.
The discovery added to an already heightened feeling that the country and Congress are in uncharted waters, said Rusty Payne, spokesman for Rep. Mary Bono, R-Palm Springs.
In a normal era, he said, Congress would be wrapping up appropriations bills to fund government operations for the coming year before going home for recess.
"It's just something we've never experienced," he said. "We don't know what's going on. We don't know what's going to happen next week. We don't have a case study."
Nichols said both houses of Congress would be in session tomorrow.
"The legislative branch will not be paralyzed by this type of activity," Nichols said.