(Reuters) -Eli Lilly said on Friday it has invested another $5.3 billion in its new Lebanon, Indiana manufacturing plant, more than doubling its previous investment, as it scrambles to meet soaring demand for its weight-loss and diabetes drugs.

The new investment, which brings the total to $9 billion, will help boost production of the active pharmaceutical ingredients (API) for Lilly's powerful weight-loss drug Zepbound and diabetes treatment Mounjaro, the company said.

"Today's announcement tops the largest manufacturing investment in our company's history and, we believe, represents the single largest investment in synthetic medicine API manufacturing in U.S. history," said Lilly CEO David Ricks.

Zepbound and Mounjaro, both known chemically as tirzepatide, are in shortage in the U.S. and expected to have limited availability across most doses through the second quarter of this year.

Zepbound was introduced in the U.S. in late 2023. Lilly has since sold more than 1.2 million prescriptions of the drugs, according to data from IQVIA.

The Indianapolis-based company expects supply of Zepbound to remain "quite tight" in the near and midterm as it ramps up capacity, it said on an investor call last month.

Lilly has committed a total of $16 billion to building new manufacturing sites since 2020, including $2.5 billion for a plant in Germany, and another $1.2 billion to update existing facilities, it said.

The company has previously said it expects the Lebanon site to begin making medicines towards the end of 2026, but for its new Concord plant and expanded facilities in Durham, both in North Carolina, to start increasing supplies of Zepbound and Mounjaro when they become operational this year.

Danish rival Novo Nordisk has also invested billions in manufacturing to ramp up supply of its popular weight-loss drug Wegovy, announcing it would take over three sites from contract manufacturer Catalent for $11 billion.

Lilly announced last month that it will acquire a manufacturing facility from Nexus Pharmaceuticals to produce injectable medicines.

The company said it expects to add 200 full-time jobs for highly skilled workers such as engineers, scientists, operating personnel and lab technicians to its Lebanon plant as part of the new investment.