Thai authorities arrested a suspect on Saturday in connection with the August 17 bombing at Bangkok's Erawan shrine on Saturday, but they say he's not cooperating and could be lying to his interrogators.

The arrest came after police raided the man's apartment, where they reportedly found bomb-making materials and more than 200 forged passports. The man's identity has not been revealed, but he has been described as a "foreigner," and police are reportedly considering the possibility that he was part of a network that provided fake passports to migrants. All of the fake passports were reportedly from the same country, but police aren't saying which one.

"He is not cooperating much. From our preliminary investigation, we think he isn't telling us the truth," National police spokesman Prawuth Thavornsiri told the Associated Press. "He told us how he entered Thailand but we don't believe everything he says."

No group has claimed responsibility for the attack earlier this month that left 20 dead and more than 120 injured, but Thai authorities reportedly believe it is unlikely that the bombing is related to international terrorism.

Prawuth suggested Sunday that the suspect was part of "an illegal network that sends people who don't have passports to third countries," and that the attack was revenge for a Thai government crackdown on people smuggling.

The unidentified suspect in the August 17 bombing at Bangkok's Erawan shrine. (Photo via Thai Royal Police/EPA)

"The police chief thinks it's personal revenge, anger from a group that is not happy with the work of officials, that we have arrested some of his people," Prawuth told the AP. "We have been very strict about getting rid of fake passports."

At a televised press conference on Saturday, Prawuth said officers found several detonators and a metal pipe with lids that they believe could have been used to construct another bomb. He said police had contacted "a number of embassies" to confirm the suspect's nationality, noting that the man speaks some English but no Thai.

Images emerged after the suspect's arrest that appeared to show his picture on a Turkish passport, but Thai authorities have avoided questions about any suspected links to Turkey, and said that the man's passport was forged.

"We don't know if he is Turkish or not," Prawuth said. "The passport you have seen is fake."

It's still unclear if the man now in custody is the same person who was seen on security footage leaving a backpack near a bench at the shrine before speeding away on the back of a motorcycle taxi. That footage, along with a sketch of a man described as "foreign" by police, was circulated shortly after the bombing. A second bomb that exploded later in the day in the city's Sathorn area caused no damage.

Thai police officers and army personnel arrested the bombing suspect at an apartment in the outskirts of Bangkok. (Photo via Thai Royal Police/EPA)

Before Saturday's arrest, Thai police had been criticized for their handling of the investigation. Authorities were quick, for example, to clean and reopen the shrine to reassure tourists and locals alike, but critics say they may have destroyed crucial evidence in their haste.

Police, for their part, have insisted progress on the case was stymied by the shrine's surveillance cameras, which were low quality when they weren't broken.

Theories about who might be behind the attack have included suggestions that it was Muslim separatists from Thailand's south, someone seeking revenge for Thailand's forced repatriation of ethnic Uighurs to China, opponents of Thailand's military government, or even rival factions within the country's security services.

On Saturday, police didn't offer validation for any of those possibilities. Instead, Police Chief Somyot Poompanmoung told reporters that authorities believe the 28-year-old found holed up in a suburban neighborhood of Nong Jok in eastern Bangkok was motivated by "a personal grudge."

"From our preliminary checks, he is related to both bombings," Thavornsiri said. "We believe he is a culprit in the same network."

The detained suspect faces charges of possessing unauthorized explosives. He is in military custody, and could be held there for renewable periods of seven days.

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The Associated Press contributed to this report.