BOSTON — The city moved ahead Sunday with plans to slowly reopen the six-block area surrounding the Boston Marathon finish line that has been cordoned off as a crime scene since twin bombs killed three people and wounded more than 180 others.

Mayor Thomas Menino said once the scene was released by the FBI, city officials will begin a multi-step process for reopening the area to the public, including environmental testing, debris removal and assessing the safety of buildings in the area.

Investigators have been painstakingly collecting evidence at the scene since the attack Monday.

“Today is the time to move forward, move the city forward,” Menino said Sunday at a news conference near the site of the bombing.

No precise timetable was given for reopening the normally bustling stretch of Boylston Street, though Ed Davis, the city’s police commissioner, said the process could begin within a couple of days.

Menino said one of the city’s top priorities in formulating the plan was respect for the victims and everyone else who was impacted by the bombing. To that end, the city announced it would temporarily relocate a makeshift memorial that was created just beyond the crime scene to Copley Square Park.

As a first step, city workers on Sunday moved the items left in the memorial — including flowers, notes and running shoes — to an adjacent sidewalk.

The city also planned to put large message boards in the area to allow people to record their own reflections on the tragedy.

The Boston Police Department said it would return any personal items found at the scene that were not being kept as evidence in the FBI investigation.

The city also planned to open a “mobile city hall” to help business owners.

In another step toward a return to normalcy for Boston-area commuters, transportation officials on Sunday reopened the Copley exit ramp off the Massachusetts Turnpike, which had been closed since the attack.

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