Three fires at homeless encampments off Nimitz Highway during sweeps by state transportation workers this week have raised concerns about damage to the freeway viaduct there.

None of the fires was large enough to cause damage, but increasing frequency of the blazes near or under the H-1 freeway’s Nimitz viaduct is worrisome to law enforcement, said Keith Kamita, an official with the state Department of Public Safety.

Sewer lines and fuel lines are also located under the viaduct, according to a state official.

State transportation spokesman Dan Meisenzahl said about 90 homeless people had been living under the freeway viaduct near Kalihi Stream. As of Thursday, workers had hauled away 50 to 60 truckloads of their belongings, including mo-ped parts, bicycles and wood from makeshift shelters.

One homeless person had a generator to power an air conditioner.

Meisenzahl said transportation workers have gone from cleaning the area once a year to every six months because of the growing number of homeless campers.

"There are no easy answers to this," he said.

Kamita said the Department of Public Safety is investigating three fires, in addition to suspected crystal methamphetamine and drug paraphernalia found during a phased cleanup.

The department provides security for state transportation workers during the cleanup.

Kamita, the department’s deputy director of law enforcement, said fires have started during previous cleanups of homeless sites, but not with this week’s frequency.

Kamita said a fire started Thursday morning, and homeless people became "a little agitated," prompting the state to call in four additional deputies to assist eight others with security.

The fire, which burned an accumulation of homeless encampment possessions, began at about 10:18 a.m. under the viaduct near a paintball field and was brought under control in 12 minutes, Fire Capt. Terry Seelig said.

Seelig said a small fire burned in the same area Tuesday and was brought under control three minutes after firefighters arrived at 6:46 a.m.

Another fire had started in a field near the westbound lane of Nimitz Highway at about 6:49 a.m. Monday. Firefighters had it under control in eight minutes, Seelig said.

Seelig said a gas can was found near the field fire.

Meisenzahl said the cleanup, involving 60 state transportation workers and 30 prison inmates, began Monday and will continue through Sept. 2.