An official at a local mosque said that police had shown him the artist’s sketch of the chief suspect in Bangkok’s worst terrorist atrocity, described by police as having Caucasian or Middle East looks. “That man has never been to our mosque,” the official told The Telegraph.

A receptionist at a seedy nearby hotel, where rooms are rented by the hour, has now told the Khaosod English website that Thai officials showed her a copy of a passport that they identified as Turkish during questioning.

“I don’t know the person in the photo,” said Suthira Rompirom of the Niagara hotel. “I have worked here for five years already. I man the daytime desk. If he checked out I would have seen him. They showed me a photocopy of a passport they said was from Turkey.”

Motorcycle taxi drivers based at a stand near the hotel said they believed they had given the man rides, but several months ago. They said that they were also shown what officials described as a copy of a Turkish passport when they were questioned.

The mosque official said that police showed him a two-page list of hotels and apartment buildings in the nearby Silom and Sathorn areas that they were approaching as part of the investigation.

There have been reports that the main suspect took a motorcycle taxi to the Silom area after the blast.

But there is no firm indication that he even spent time in Bangkok before the bombings as he was driven to the Erawan shrine from the city’s main railway station by a tuk-tuk driver.

Mystery surrounds the motives for the blast and who was behind it. The Thai police have said they believe the chief suspect is a foreigner, but the country’s ruling junta has also insisted that the blast is not believed to be linked to international terrorist groups.

The possible Turkish connection has raised fresh speculation in Thailand that the blast may have a link to the Uighurs, an ethnic Turkic Muslim population in western China.

For the junta recently deported more than 100 Uighurs to China, despite strong protests that faced the risk of persecution there. But the scenario has so far been little more than speculative.

British and American intelligence agencies have been working with their Thai counterparts amid concerns that the attack could have been the work of Islamic terrorists.

Bangkok is known to have been used as a transit point for Islamic radicals and there have long been concerns that it could be a “soft target” for terrorists.

But there has been no claim of responsibility for the attack, which would have been expected from a group such as the Islamic State faction or al-Qaeda affiliates. And the blast killed Thais and ethnic Chinese tourists from other Asian countries, rather than targeting a site popular with Western visitors.

There has also been speculation that it could be linked to the country’s decade of domestic political turmoil, rifts within the ruling military or a long-running Malay Muslim insurgency in the south.

In a separate development, police said they were searching for a man shown in newly-released surveillance video at the scene of a second blast in the capital.

The CCTV footage could offer fresh clues as the country accepted an offer from the US to provide facial recognition technology to try to identify the chief suspect seen apparently planting the bomb that killed 20 people at the Erawan shrine.

The new surveillance footage was recorded at Bangkok’s riverfront less than half an hour after the explosion ripped threw crowds three miles away at the Erawan shrine on Monday evening

It shows a man in a blue shirt placing a bag on a small bridge, then using his smart phone before kicking the bag into the water near a busy pier.

At about 1pm the next day, an explosion took place in the water at the same location, sending a huge plume of spray over terrified by-passers but causing no injuries.

Police explosive experts have said the same sort of pipe bomb was used in both incidents, although they are still investigation any connection between the two blasts.