Auditors arrived at the Panama Ports Company on Monday "to begin an exhaustive audit aimed at ensuring the efficient and transparent use of public resources," the comptroller's office said on social media.

The company, part of Hutchison Ports, a subsidiary of Hong Kong-based conglomerate CK Hutchison Holdings, operates the ports of Balboa and Cristobal at the canal entrances.

The comptroller's office said the aim was to determine whether the company was complying with its concession agreements, including adequate reporting of income, payments and contributions to the state.

Trump, in his inaugural address Monday, repeated his complaint that China was effectively "operating" the Panama Canal through its growing presence around the waterway, which the United States handed over at the end of 1999.

"We didn't give it to China, we gave it to Panama. And we're taking it back," he said.

Trump has been raising pressure for weeks over the canal -- through which 40 percent of US container traffic travels -- and has repeatedly refused to rule out military force against Panama, historically friendly to Washington.

Panamanian President Jose Raul Mulino swiftly denied that any other nation was interfering in the canal linking the Atlantic and Pacific Oceans, saying his country operated it through a principle of neutrality.

"The canal is and will remain Panama's," Mulino said.

Panama Ports Company's concession agreement was extended by 25 years in 2021.

The United States is the canal's main user, followed by China.

Since 2000, the waterway has contributed more than $30 billion to Panama's state coffers, including nearly $2.5 billion in the last fiscal year.

Even so, Panama's comptroller general, Anel Flores, said recently that "Panamanians deserve a little more respect and a little more resources," referring to the port operator.