BANGKOK (THE NATION/ASIA NEWS NETWORK) - Thai security officials are checking guesthouses, apartments and places popular among foreigners in their bid to catch the suspected bomber behind the deadly Erawan Shrine blast.
The blast killed 20 people and injured more than 100 last Monday.
"There are more than 10,000 places in Bangkok that we have to inspect and search," Metropolitan Police chief Lieutenant-General Srivara Ransibrahmanakul said. "We may also need to repeat searches at some places."
Lt-Gen Srivara said investigators had interviewed more than 10 witnesses and planned to interview all survivors of the blast.
Asked about Japanese media reports that the suspected bomber was a Spanish man, Srivara said he had not yet seen those reports.
No arrest has been made yet in connection with the blast, described as the worst ever attack on Thai soil.
National police chief Somyot Poompanmuang said on Sunday that all relevant officials had been working hard to solve this case.
"We have had a clear focus. It's just that we can't disclose details at this time," he said.
He said the delay in the investigation was related to the lack of modern equipment, not the ability of officials.
Mr Somyot spoke after overseeing the start of the "searching the city to crack down on criminals' dens" operation. Participating in the Bangkok-based operation were the police, soldiers and Bangkok Metropolitan Administration police.
The operation was aimed at restoring local residents' and tourists' confidence in the wake of the blasts, he said.
Asked if police knew who was behind the shrine attack, Mr Somyot said: "We have had some information. Some of those involved are still in Thailand."