Explosives experts have removed all hazardous materials from the apartment of the suspect in the Colorado shooting, police said Saturday evening, hours after telling reporters they found “multiple booby traps” and improvised explosive devices in the home.

The Aurora Police Department announced the development in a statement on Saturday evening, saying that “all hazards have been removed,” and have been taken to “a disposal site.”

“The FBI Evidence Response Team (ERT) remains on scene processing the apartment for evidence,” the statement read. “This will be the case for several more hours.”

According to the statement, the ERT will continue its work on Sunday.

Meanwhile, Aurora police also said that all area residents are now allowed to return home, except for those living in the suspect’s apartment building.

Throughout Saturday, explosives experts carefully neutralized booby traps and a number of explosives at the home of James Holmes, the suspect in the shooting that left 12 people dead and dozens more injured.

In an update for reporters Saturday afternoon, FBI Special Agent James Yacone said a robot was first sent into Holmes’s apartment to neutralize a booby trap, a wire that had been set up across the front door.

Bomb technicians then began moving through the apartment, where they found potentially liquid accelerant and fuel, as well “multiple booby traps and improvised explosive and-or incendiary devices that were contained inside the residence,” Yacone said.

Before Yacone updated reporters, investigators triggered a “controlled detonation” at the apartment, before warning that more explosions could follow.

Police blasted an air horn three times and warned nearby journalists to stand behind their vehicles as bomb squads carried out the detonation.

Holmes, 24, was arrested Friday after a mass shooting at a movie theatre in Aurora, a suburb about 16 kilometres east of downtown Denver. Twelve people were killed and 58 others injured.

Aurora Police Chief Dan Oates said during the Saturday afternoon news conference that Holmes’s apartment was booby trapped to kill “whoever entered it.”

Oates told reporters that evidence suggests the brazen shooting was planned well in advance.

“We've become aware that he had a high volume of deliveries to both his work and home address. We think this explains how he got his hands on the magazine, ammunition," Oates said. "We also think it begins to explain how he got the materials he had in his apartment.

"What we're seeing here is evidence of some calculation and deliberation," Oates added.

Police evacuated Holmes’s apartment building and surrounding residences the same day that he was arrested after spotting what appeared to be an extensive booby trap and jars of ammunition.

Oates said that the shooter used a semi-automatic rifle, a shotgun and a pistol to gun down theatregoers. It appears Holmes had purchased the weapons at local gun stores in the past two months.

Holmes had also purchased 6,000 rounds of ammunition online, Oates said.

Meanwhile, Aurora police went door-to-door late Friday informing families that their loved ones were among those killed when gunfire erupted during a midnight screening of the latest Batman installment “The Dark Knight Rises.”

Seven shooting victims remain in hospital with a variety of injuries, trauma surgeon Bob Snyder of the Medical Center of Aurora confirmed on Saturday.

Of those patients, three are on a regular trauma floor and four are in the intensive care unit. Two of the ICU patients are in critical but stable condition, he said.

“We actually have plans to move one of our patients in the ICU out to the floor today,” Snyder told reporters.

Part of the recovery process will be psychological, he said, as patients come to accept injuries that may present them with challenges for the rest of their lives.

“Today’s the day that there’s going to be some realizations that there is going to be some serious long-term issues that people are going to have to deal with,” he said.

Late Saturday, the White House announced that U.S. President Barack Obama will visit victims and their families on Sunday.