More than 50 people from the mainland are to be charged with working illegally in the Philippines after they were arrested in a series of raids. A spokeswoman for the Bureau of Immigration, Elaine Tan, said that the suspects had been working on tourist visas. The mainlanders were arrested on Tuesday in three separate raids conducted by the bureau in and around the capital, Manila. Twenty-nine Chinese nationals had been working at a retail business in the capital. The rest were employed as construction workers in neighbouring Quezon City and Malabon City. Tan denied that the arrests were connected to increased tensions between the Philippines and the mainland over rival territorial claims in the South China Sea. She said the investigations were part of the regular work of the bureau. "It has no connection to the tensions with China. This is just coincidental," she said. "We are in touch with the consul as to the documents of their nationals. If a foreign national fails to present any document to support his employment, he will be issued the necessary charge sheet and will eventually be deported." The process could take at least a month, she said. Tan said the bureau had acted on a tip-off, but declined to give any details. The Chinese embassy in Manila yesterday said in a statement that it had sent its counsel to visit the detained Chinese nationals and had demanded that they be treated fairly by Filipino authorities. The largest labour group in the Southeast Asian nation, the Trade Union Congress of the Philippines, asked the government last week to investigate the rising number of illegal workers from overseas in the country. The labour group said that two weeks ago the immigration bureau had arrested 50 mainlanders, and an Australian and a British national working without employment permits at a power plant construction site in Davao City. Chinese without work permits are not allowed to work in the Philippines. The Chinese-language newspaper World Times said some had been detained for overstaying their visa and running retailing businesses.