Hyundai Heavy Industries Co. paid about $187,000 to free four abducted South Korean workers and their local colleague, a lucrative ransom showing the continuing allure of kidnapping in Nigeria's oil-rich southern delta, police said Friday.

South Korean officials declined to say whether they paid a ransom when announcing the hostages' release on Dec. 22, following the pattern of other foreign governments and companies operating in the Niger Delta when dealing with abductions. However, cash payments often represent the only safe way of getting back expatriate workers in the region since militants began attacks there in 2006.

Police learned of the kidnapping payment after arresting one of three suspected kidnappers, Bayelsa state police spokesman Fidelis Odunna told The Associated Press on Friday. The man claimed that several gangs involved in the kidnapping received 30 million naira ($187,500), Odunna said.

"The real reason for the kidnapping is for financial interest," the spokesman said. "The company didn't want to endanger the lives of the workers and paid secretly."

While the workers were safely released, Odunna said the cash payment likely would further embolden the criminal gangs and militant groups — some often one in the same — that operate in the delta, a region of mangroves and swamps about the size of Portugal.

On Dec. 17, gunmen ambushed workers for the Korea-based company at a construction site in the Brass region of Bayelsa state. Six people were initially taken, though kidnappers let one Nigerian go an hour after the attack, likely because he came from the area, authorities had said.

Foreign companies have pumped oil out of the Niger Delta for more than 50 years, making Nigeria one of the top crude suppliers to the U.S. Despite the billions of dollars flowing into Nigeria's government, many in the delta remain desperately poor, living amid polluted waters without access to proper medical care, education or jobs. The poor conditions sparked an uprising in 2006 by militants and opportunistic criminals who blew up oil pipelines and kidnapped foreign workers.

That violence ebbed in 2009 with a government-sponsored amnesty program that offered ex-fighters monthly payments and job training. However, few in the delta have seen the promised benefits and sporadic kidnappings and attacks continue. Pirates operating in the region also routinely kidnap foreign sailors off vessels in the Gulf of Guinea.

Middle- and upper-class Nigerians now routinely find themselves and their family members targeted by kidnap gangs. The end of the year in Nigeria usually sees an uptick in criminal activity as well, as criminal gangs target the wealthy returning to the country to celebrate the holidays.

Most workers taken hostages are released after a few weeks when their employers pay a ransom, typically around a $100,000 or higher, depending on negotiations, experts say.