Honolulu city inspectors are investigating the collapse of a metal railing at Ala Moana Center, where a 21-year-old man fell four floors to his death and another was critically injured Sunday night.

Authorities said both victims were leaning on a railing that gave way. They fell to the ground on the mauka side of the shopping center near Barnes & Noble at about 10 p.m Sunday.

Nicholas Freitas of Honolulu died in the fall, and the other man was in critical condition, according to authorities. Freitas was a graduate of Roosevelt High School. His family declined to comment on the incident.

City Department of Permitting and Planning spokesman Curtis Lum said the department’s investigation began Monday.

“It’s probably going to take a while,” said Lum, who said he didn’t know when the railing was installed at the shopping center.

Meanwhile, Honolulu police are also investigating, and Ala Moana Center General Manager Francis Cofran said the center is cooperating with them.

Cofran expressed condolences but declined to comment further pending the investigations.

Ala Moana Center is owned and managed by General Growth Properties Inc., whose headquarters are in Chicago.

The firm specializes in owning, leasing and redeveloping high-quality retail properties in the United States.

Sunday’s incident occurred in an older section of the state’s largest shopping center, which has more than 340 stores and restaurants. This summer the center completed a multilevel 650,000-square-foot expansion of its Ewa Wing.

In 2000 a 19-year-old Hawaii Pacific University freshman died and his 18-year-old girlfriend was critically injured after leaning on a railing that gave way on the 11th-floor balcony of the Ala Moana Tower apartments on Kapiolani Boulevard.