Colombo - Police have launched an inquiry into his departure.
The Sri Lankan government has put airports on alert to stop police detectives leaving without permission after a top officer who had reportedly received death threats fled the island, police said on Tuesday.
The alleged threats against inspector Nishantha Silva came after the November 16 election of Gotabaya Rajapaksa, who was also under investigation by him.
Police spokesman Ruwan Gunasekera said the names of 704 Criminal Investigation Division (CID) officers had been sent to immigration authorities.
"The move is to ensure that no officer leaves the country without following the proper procedure of obtaining permission for overseas travel," he said.
The directive came after Silva left Sri Lanka on Sunday, reportedly seeking asylum in Switzerland.
Police have launched an inquiry into his departure.
Silva's investigations included high profile killings and corruption involving administration members under former president Mahinda Rajapaksa, brother of the new president, who ruled for a decade until 2015.
Among the cases was the 2009 assassination of editor Lasantha Wickrematunge by an alleged hit squad.
Mahinda Rajapaksa has returned to power as prime minister after leading his younger brother's successful election campaign.
Police said Monday there were allegations Silva had conducted biased investigations in the past four and a half years.
He was removed from his CID post last year after Mahinda Rajapaksa briefly served as prime minister, but he was restored after that administration collapsed.