At a press conference Tuesday morning not far from the site of Monday's Boston Marathon bombing , officials from local, state, and federal law enforcement dispelled some of the many false reports about the incident and requested assistance from the public with the investigation.

Boston Mayor Thomas Menino stressed despite reports of numerous unexploded devices at the scene that all parcels had been examined and there were only two bombs both of which were detonated in the attack. FBI Special Agent Richard Deslauriers, who is directing the investigation, said that no one was in custody.

Officials said "176 casualties had presented at area hospitals." Out of this number 17 cases are critical. Three people were killed in the attack. None of the victims is believed to have been a perpetrator of the bombing.

Boston Police Commissioner Edwin Davis said the area of the bombing had been swept twice by explosive ordnance teams before the bombing.

Investigators are urging the public to supply them with any photos or videos of the crime scene taken right before, during, and immediately after the bombings. In addition, Commissioner Davis said that all private and public surveillance video of the area had been taken into evidence, and it was being "examined frame by frame" by forensic experts from the FBI.

Special Agent Deslauriers asked the public for patience and cooperation.

Boston officials said streets in the area would be closed for at least two days, but they are working on "collapsing the crime scene" down to a much smaller area.

In addition, Boston area residents and visitors should expect to see "heightened police presence" for the next few days. Officials said the increased law enforcement presence was for the comfort and reassurance of the public not because of any imminent threats, and it includes Boston officers, state police, and National Guard. Help has also been extended to Boston authorities from New York, Baltimore, Chicago, Los Angeles, and other cities.