MADISON, Wis. -- Authorities are investigating three suspicious items found around downtown Madison on Wednesday.

SLIDESHOW: See Photos From Webster/Main Scene

Police said that two suspicious items removed from Madison's sewer system aren't related to an investigation into a string of pipe bombs found in a parking ramp in recent weeks.

At a late-afternoon press conference, police spokesman Mike Hanson said that two of the items were uncovered by a bomb squad in the sewer system about a block from the state Capitol. The objects were removed at the intersection of Webster and Main streets.

These two objects were described as resembling piping, WISC-TV reported.

Buildings in the area weren't evacuated, but people in the buildings were asked to move away from the corners facing the location.

Witnesses said that they saw someone drop something in sewer and walk away, WISC-TV reported.

In this incident, authorities said that they are looking for a white male with a thin build, balding, in his late 40s, wearing dark clothes, a green baseball cap and carrying a white bag. Officers are searching the area, looking for man fitting the suspect's description.

Separately, Hanson said that a suspicious package was found in a post office box several blocks away in the 400 block of West Doty, near Broom. That package was discovered by a postal carrier one block from a downtown parking ramp for state and municipal employees where the other three pipe bombs have been discovered since November.

Hanson said that authorities are analyzing the items now.

In each of the incidents, calls were made to police about suspicious behavior and authorities are asking for people to be vigilant.

"All of this is in relation to someone seeing suspicious activity and then, not only is the person suspicious but they have something with them and out of the ordinary. This is textbook for what we're asking for," Hanson said.

Hanson said that police are looking for two different suspects.

The first incident was reported just before noon. Police cordoned off several blocks of downtown and prohibited foot traffic for most of the afternoon, causing gridlock downtown.

Hanson said the task force that's investigating the pipe bombs found in the parking ramp is leading Wednesday's investigation.

Stay tuned to WISC-TV and Channel 3000 for continuing coverage.