Construction of the 55km bridge connecting Hong Kong, Macau, and mainland China involves the building of artificial islands, new roads, and an undersea tunnel. Photos taken earlier this month showed a jagged shoreline around one of the islands as wave-absorbing concrete blocks appeared separated from the protective barrier and partly submerged.

The photos have prompted concern about the structural integrity of the island, built by a Chinese contractor, which connects the bridge to an undersea tunnel. Hong Kong’s highway department sent its director of highways to the mainland city of Zhuhai to meet project officials, and has said it would monitor the works of the bridge to ensure “quality meets the relevant requirements”.

In response to the release of the photos, officials at the Hong Kong-Zhuhai-Macau Bridge Authority in Zhuhai said the placement of the blocks was by design.

“We have our ways to do it, and you [Hong Kong] may have your ways to do it. You seem to presume that part of the structure had sunk … but it has been designed as such. We do not think there is any problem with that. There are rules and standards for us to follow,” said the authority’s deputy director Yu Lie, according to the Hong Kong-based paper, the South ChinaMorning Post.

Previously the bridge authority said the blocks, known as “dolosse” were purposely arranged in a “random manner” to alleviate pressure on the undersea tunnel.

The project, now in construction for nine years, has been dogged by delays, lawsuits and budget overruns. The bridge, originally slated to open in 2016, is expected to be operational sometime this year, according to Hong Kong officials.

Supporters of the project say that by connecting the three cities of Hong Kong, Macau and Zhuhai to China’s Pearl River Delta region, the area will emerge as a major economic hub. Critics say the bridge is just another way for China to tighten its hold over Hong Kong, a semi-autonomous special administrative region that has chafed under Beijing’s authority.

The bridge authority also released photos of the island before and after the deadly Typhoon Hato last August to show that the blocks’ protective functions had worked.

Hong Kong’s top official has also tried to assuage concerns. Chief executive Carrie Lam said on Friday that the “stability of construction works is a scientifically proven thing.”

“I hope that just because some individuals have taken photos or made some comments, that everyone will not jump in and doubt the project’s design,” she said.

More about: #Sea-Bridge