The return home of the last group of South Koreans from a suspended inter-Korean industrial complex in North Korea was being delayed Monday for reasons that were not clearly explained.

More than 400 South Korean workers and managers have returned home since April 9 when North Korea unilaterally withdrew all of its 53,000 workers from the South Korean-run factory zone in the North's border city of Gaeseong in anger over U.S.-involved military exercises in the South.

The last group of 50 South Koreans, who include some state-run Korea Electric Power Corp engineers, had originally been scheduled to cross the border before 5 p.m. but their trip has been held up, according to the Unification Ministry which handles inter-Korean affairs.

"The two sides are currently in the process of ironing out some details," a unification ministry official said without elaborating. He indicated that the pending issues were not insoluble.

According to government sources, differences were about taxes and ownership of hundreds of vehicles jointly run by the two sides at the complex. Other unresolved issues include how to handle inventories of raw materials and other properties left, they said.

In a tit-for-tat, South Korea on Friday decided to pull all of its workers from the industrial complex after North Korea turned down its offer for dialogue to resolve the standoff over what has been billed as the last remaining symbol of inter-Korean cooperation.

Once all South Koreans are pulled out, Seoul is expected to cut off electricity and water supply to the complex. South Korea had set up power lines that could provide a maximum 100,000 kilowatts of electricity to Gaeseong.

South Korean damages from the trouble are estimated at 2.8 trillion won ($2.5 billion), according to the association of 123 South Korean companies that have invested in Gaeseong.

The figure is much higher than 1 trillion won estimated by Prime Minister Chung Hong-won in his testimony to the National Assembly last week.

Gaeseong is a product of the 2000 summit meeting between late South Korean President Kim Dae-jung and then North Korean leader Kim Jong-il.

It has survived until now despite heightened border tensions between the two Koreas.

Meanwhile, a senior official at the presidential Cheong Wa Dae made clear the North is to blame for the crisis, saying that South Korea has no intention to make concessions.

"There will be no incentives given or concessions made to resolve this issues," said Hong Yong-pyo, presidential secretary for unification affairs. (Yonhap News)