The land at the southeastern coast of the Penang island was under the care of the Fisheries Department.
State Environment Committee chairman Phee Boon Poh said a high-level team from the state Forestry Department was despatched to the site, while the district officer was summoned for an explanation.
“The state has committed to protecting our mangrove forests and to have this going on, is very upsetting.
“Stern action will be taken if they are found to have gone against the law,” Phee told FMT.
Batu Maung assemblyman Halim Hussain, who is also part of the state leadership, had earlier alerted Phee about scores of lorries carrying earth entering the mangrove land area.
Halim told FMT that the size of the cleared land could be as big as a football field, but said he would only comment further after getting a report from agencies concerned.
He said the mangrove land was “rented out” by a federal agency to a private company.
In October, mangrove forests on the Juru coastline on mainland Penang were illegally cleared, as highlighted by Bukit Tengah assemblyman Gooi Hsiao Leung, who urged the state government to gazette the Sungai Belanak area to protect what was left of the mangrove land.
Clearing mangrove land is illegal under the National Forestry Act 1984 and the National Land Code 1965.
According to the Consumers Association of Penang (CAP), Penang had around 3,500ha mangrove swamplands in the 1950s.
Today, it estimated that only around 400ha of mangrove land was left. Most of it has been cleared for agriculture, industries and housing since the early 1990s.
CAP president SM Idris said mangrove forests are important to islands like Penang, acting as a buffer for natural disasters such as tsunamis.
He said in 2004, the mangrove forests helped reduce the impact of the disastrous tsunami which hit large parts of the Indian Ocean.
According to Idris, a major culprit is the aquaculture industry, where forests are illegally cleared for fish farming.
The Forestry Department estimates that mangrove forests in the country have been reduced by 30% between 1975 and 2000.