Rights groups including Amnesty International on Thursday urged Qatar to disclose the whereabouts of a Kenyan man who has written about migrant rights in the Gulf state and who was arrested by security officials last week.

Malcolm Bidali, who writes under a pseudonym, was taken from his accommodation on May 4 for questioning by the state security service and it is not known where he is being held, they said.

A joint statement from Amnesty International, Human Rights Watch, MigrantRights.org, FairSquare and the Business and Human Rights Resource Center said “Malcolm is a security guard, blogger and activist, who has been vocal about the plight of migrant workers like himself and has written for a number of online platforms.”

“A week before his arrest, Malcolm gave a presentation to a large group of civil society organizations and trade unions about his experience of working in Qatar,” they reported.

Light has been shed on the country’s human rights record as it buckles down to host the 2022 soccer World Cup, particularly over the conditions of migrant workers. Doha has launched labor reforms that have sought to address some concerns.

The groups noted that in response to a joint request from them, Qatar’s government confirmed the man’s arrest and said he is under investigation for breaching Qatar’s security laws and regulations, without revealing his whereabouts.

“We are extremely concerned for his well-being, and that he may have been detained in reprisal for his legitimate human rights work. If Malcolm is detained solely for peacefully exercising his right to freedom of expression, he must be released immediately and unconditionally,” the joint statement said.