Many Rohingya have been seeking in recent weeks to leave by sea from Bangladesh - where they live in squalid refugee camps after fleeing their mostly Buddhist homeland Myanmar - before the monsoon season starts in earnest.
Security forces have prevented hundreds from departing for Malaysia with people smugglers on fishing boats. But last month 34 Rohingya arrived in the northern Malaysian state of Perlis, the first group believed to have landed in the country in almost year.
On Monday police detained 41 Rohingya men - aged 14 to 30 - who arrived by sea in the same area the last boatload landed, and are hunting for another six believed to have come ashore, local police chief Noor Mushar Mohamad told AFP.
About 200 more are thought to be trapped at sea in Thai waters, said the police chief, citing testimony from migrants.
"This is definitely the work of human smuggling syndicates working with local syndicates," he said.
"I fear there could be more Rohingya arrivals unless maritime enforcement agencies step up patrols urgently."
Noor Mushar said initial investigations indicated those who came ashore travelled in a large boat before being transferred to smaller craft by local criminal gangs and ferried ashore.
According to testimony from one migrant, the Rohingya paid 4,000 ringgit ($975) each, and were dropped off a short distance from the coast and walked to shore, he said.
The 41 detained have been handed over to immigration authorities, he said. It was not clear whether they had departed from Bangladesh or Myanmar, or when they had arrived.
About 740,000 Rohingya fled Myanmar for Bangladesh following a brutal military clampdown in their home country in August 2017, joining hundreds of thousands already living in crowded camps.
The traditional route to Malaysia is by boat from Myanmar or Bangladesh. Refugees arrive either in Thailand and head overland to Malaysia, or arrive directly in Malaysia.
But arrivals have fallen markedly since 2015 when Thailand launched a crackdown, which disrupted the lucrative trade and led to smugglers abandoning huge numbers of refugees at sea.
Relatively affluent, Muslim-majority Malaysia has long been a favourite destination for Rohingya, where they are a source of labour in low-paying industries such as agriculture and construction.
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