SEOUL, South Korea >> South Korean authorities are questioning 31 North Koreans held after their boat strayed into South Korean waters over the weekend near the front-line island attacked by the North late last year, reports said Monday.

It was not immediately clear whether the 20 women and 11 men were attempting to defect to South Korea or were fishing when their boat drifted south, Seoul’s Yonhap news agency said, citing an unidentified government official. South Korea’s Dong-a Ilbo newspaper carried a similar report.

The 5-ton motorboat crossed the Koreas’ western sea border and landed on Yeonpyeong Island on Saturday, Yonhap said. The Dong-a Ilbo report said the boat was stopped near the island and towed to the western port city of Incheon by the South Korean military, who were questioning the occupants.

Officials from the Unification Ministry, military and National Intelligence Service in Seoul said Monday they could not confirm the reports.

Yeonpyeong Island lies just 7 miles from North Korean shores. The artillery attack in November that killed four South Koreans was one of the worst attacks on the South since the three-year Korean War ended in a truce in 1953.

More than 20,000 North Koreans have defected to South Korea, most via China, since the war left the Korean peninsula divided by a heavily fortified border. Defections have surged in recent years amid economic hardship in North Korea, with more than half of the defections occurring over the past three years, according to the South Korean government.

However, the fishing boat seized Saturday may have drifted south due to fog or ocean currents, Yonhap quoted some officials as saying. No children were on board, reports said.

The western waters teem with seafood, and North Korea has long disputed the Yellow Sea border drawn by U.N. forces in 1953.

In the past, North Koreans who crossed the border in similar circumstances have been interviewed by the South to determine their intentions. The South has accepted those who chose to defect and repatriated those who wanted to return to North Korea.

The reports come on the eve of preliminary defense talks between the Koreas that would precede higher-level defense talks on how to ease tensions on the peninsula. The talks would be their first official dialogue since the November attack.