HONOLULU -- A day after a box jellyfish invasion shut it down, Hanauma Bay is open again.

No jellyfish were found washed up on the shoreline Friday morning, Hanauma Bay manager Alan Hong said. However, he added that the situation will be monitored closely if people get stung by jellyfish offshore.

The bay was closed Thursday at 11 a.m. after 14 stings were reported in an hour.

In Waikiki, only 40 box jellyfish were found washed up on shore Friday morning. Ocean safety officials counted more than 1,000 Thursday morning.

The jellyfish usually show up when they mate, seven to days after a full moon. They can cause a painful sting, which can be dangerous to those allergic to the toxins.

More than 50 stings were reported in the Kapahulu Groin area by Thursday midmorning, according to lifeguards. A few people had to be treated by emergency medical personnel, including a visitor from Korea who was stung on her face, arms and back while swimming off Kuhio Beach.

Although there were fewer jellyfish found on shore, the city's ocean safety division still has an advisory issued for south shores of Oahu. Warning signs will be posted if lifeguards find jellyfish. Swimmers are advised to check with lifeguards, who are also equipped to treat the stings.

This month's influx was reported to be the third largest in the last nine years. Most of the jellyfish should be gone by Saturday, ocean safety officials said.