The corruption scandal around an economic-development fund in Malaysia is spilling beyond the country’s borders, as officials at a United Arab Emirates state investment vehicle raise questions about more than a billion dollars in money that they said is missing. Abu Dhabi has long been a source of support for the fund, 1Malaysia Development Bhd., which was set up six years ago by Malaysian Prime Minister Najib Razak to develop new industries in the Southeast Asian country. Now, as 1MDB tries to fend off a cash crunch, its backers in Abu Dhabi are asking what happened to a $1.4 billion payment the fund said it made but which they never received, two people familiar with the matter said.

The dispute comes as Mr. Najib is battling a separate scandal linked to 1MDB. Malaysian investigators are examining the transfer of hundreds of millions of dollars into the prime minister’s alleged private bank accounts through entities linked to 1MDB. The disclosures have sparked a political crisis and set off a handful of investigations around the world, destabilizing the government and damaging confidence in Malaysia’s economy.