Senior inspector Lam Yuen-yee, 37, commander of the police Small Boat Unit, and three other officers were thrown into the water after their marine interceptor capsized on Saturday while patrolling Sha Chau island in the northwest waters of Hong Kong.

Lam, nicknamed "Kryptonite of smuggling," has busted smuggling cases over the years, including one involving HK$37 million worth of animals and goods in August last year. The three male officers - a sergeant, a foreign senior inspector and a constable - were rescued and conscious when sent to Tuen Mun Hospital.

The interceptor with Lam and the three men chased a speedboat suspected to be smuggling frozen meat into the mainland but it escaped into mainland waters.

During the chase, the speedboat made a U-turn, hitting the stern of the interceptor, which overturned.

Two officers rose to the surface while awaiting rescue. Lam and the other officer were trapped underneath the overturned interceptor.

Later, another marine vessel rescued the other officer from underneath the interceptor. Lam was suspected to have been dragged away by currents.

Marine police, fire services divers and drones were searching for Lam in Sha Chau, Lung Kwu Tan and Lung Kwu Chau. Two Government Flying Service helicopters also flew over Sha Chau and the Hong Kong-Zhuhai-Macau Bridge to search for Lam.

Fourteen maritime vessels from the mainland joined the rescue operation in mainland waters.

Sources said the four officers - including Lam - were all wearing life jackets.

Born into a grassroots family, Lam, who is married, started as a constable before being transferred to Tuen Mun's crime squad, sources said.

Described as hardworking, Lam rose quickly through the ranks to become an inspector in three years. In 2015, she became a senior inspector and was transferred to the Marine Police. Last year, Lam joined the Small Boat Unit. She is also a member of the police football team.

Meanwhile, dozens of suspected smuggling speed boats were seen approaching the Hong Kong-Zhuhai-Macau Bridge, in a video by a former marine police officer.

In the three-minute clip by "Les Bird" posted on Friday, the boats are seen speeding by the bridge, with one driver in each and no number on the hull.

Police and customs' operations have been more frequent in Sha Chau - a smuggling blackspot - as syndicates are turning to waterways to smuggle goods during the pandemic.

In January last year, three customs officers died after their craft overturned while chasing suspected smugglers.

In the first eight months of this year, HK$480 million worth of contraband in cross-border maritime smuggling cases have been seized, customs say.