Bithumb, South Korea's second-largest cryptocurrency exchange, accidentally distributed 620-thousand bitcoins to hundreds of users during a promotional event, triggering a sudden bitcoin price drop.

According to industry sources, Bithumb planned to airdrop a small reward of two-thousand won, or roughly one dollar and 36 cents, or more to users as part of the event at 7 p.m. Friday.

Rather than sending bitcoins worth a total 620-thousand won to 249 participants, the exchange gave away 620-thousand bitcoins by mistake, or an average two-thousand-490 bitcoins valued at 244 billion won per user.

Though Bithumb halted trading and withdrawal from affected user accounts by 7:40 p.m., the bitcoin price temporarily plunged to 81-point-one million won after some users immediately sold the received bitcoins.

The price climbed back above 98 million won a few minutes later.

In a statement issued at around midnight, Bithumb apologized for the mistake and said it recovered 99-point-seven percent of the bitcoins right away.