SANTIAGO - More than 50 companies have expressed interest in developing lithium projects in Chile, Finance Minister Mario Marcel said on Tuesday, after the government called for proposals for a range of salt flats containing the battery metal.

Chile, the world's largest copper producer, called for proposals in April to develop lithium projects in more than two dozen salt flats that have yet to be fully explored, while reserving the Atacama and Maricunga brine deposits for state control.

Fifty four firms from 10 countries submitted statements of interest to develop 88 projects through the public process, which ended on Monday, Marcel said at an event in Santiago.

"There are investors of different sizes ... there are local investors and many foreign investors," Marcel said. "There is clearly a very broad interest in investing in this industry."

The mining ministry will later provide details on the salt flats that have received overlapping proposals.

In April, Chile's mining minister said there would be a tender process if more than one company expressed interest in a single site.

Investors have, however, raised concerns about how the government will award lithium contracts in salt flats where mining concessions have previously been granted, which risks creating a kind of double ownership.

Chile is seeking to build its role in the lithium industry, which is the world's second largest after Australia, through state-led projects as well as private investment.

The US ambassador to Chile, Bernadette Meehan, said at an event in Santiago on Tuesday that US companies have shown "intense interest" both in extracting lithium and in producing components that use the material, such as batteries.

"There are US companies and Western companies interested in all lithium opportunities announced by the government of Chile," she said.

Currently, only US firm Albemarle and local miner SQM produce lithium in the country. Last month, SQM signed an agreement with state-run giant Codelco to launch a majority state-run joint venture in the Atacama salt flat. Codelco is also seeking a partner for a major new lithium project in the Maricunga salt flat.