TOKYO -- Police investigating an expressway-tunnel ceiling collapse that killed nine people searched the offices of the tunnel operator Tuesday to see if there is any evidence that the company neglected safety.

Hundreds of concrete slabs collapsed Sunday deep inside the Sasago Tunnel west of Tokyo, falling on three moving vehicles. The accident is raising calls for more spending on Japan's aging infrastructure.

The tunnel, a major link between Tokyo and central Japan, opened in 1977 at about the peak of the country's postwar road construction boom. Central Nippon Expressway Co., its government-owned operator, said it had no record of any repairs performed since then, but company official Satoshi Noguchi said an inspection of the tunnel's roof in September found nothing amiss.

Authorities early Tuesday raided several of the company's offices, including its headquarters in the central city of Nagoya. About a dozen uniformed police were shown on television entering the headquarters, toting cardboard and plastic boxes.

"Yes they are searching our offices here. We will be fully cooperating with them," said Osamu Funahashi, another company official.

The transport ministry, meanwhile, has ordered inspections of 49 other highway and road tunnels of similar construction around the mountainous country.

An estimated 270 concrete slabs suspended from the arched roof of the tunnel, each weighing 1.4 metric tons (1.54 short tons), fell over a stretch of about 110 meters (120 yards), Noguchi said. Two people suffered injuries in the collapse.

The operator was exploring the possibility that bolts holding a metal piece suspending the panels above the road had weakened with age, he said. The panels, measuring about 5 meters (16 feet) by 1.2 meters (4 feet), and 8 centimeters (3 inches) thick, were installed when the 4.7-kilometer-long (3-mile-long) tunnel was constructed in 1977.

Crews had to stop recovery work Monday in the tunnel about 80 kilometers (50 miles) west of Tokyo because the roof needed to be reinforced to prevent more collapses, said Jun Goto, an official at the Fire and Disaster Management Agency.

By Tuesday, crews were removing the concrete slabs from the tunnel, said Goto, who added that authorities do not expect to find any more victims inside. ---

Associated Press writer Elaine Kurtenbach contributed to this report.

Associated Press