America's Federal Emergency Management Agency (FEMA) is pursuing thousands of homeowners for millions of dollars in disaster recovery funds that were issued in error after Superstorm Sandy.
FEMA gave out $1.4bn (£875m) in individual grants after the devastating weather system hit America's east coast two years ago.
The New York Legal Assistance Group now estimates that at least 10,000 people are being asked to pay back more than $5m.
Individuals can be asked for anything up to $30,000, repayable within a few months.
Often the first time they realise their case is being reassessed is when a letter demanding money drops on to their doormat.
The letter can't be ignored. Those who do not pay FEMA back find themselves in debt to the federal government, which can take money from pay and from tax rebates to claw its money back.
Many of those receiving the demands are on middle-to-low incomes, and many are still living in communities not fully recovered from the devastation wreaked by the storm.
The process is called a "recoupment", which is the term used by FEMA when it tries to recover funds issued to a household that may have received more than it was allowed under programme rules.
By law, FEMA does not have to specify whether it was at fault for granting the money or whether it believes the individuals claimed in error.
The New York Legal Assistance Group is using its storm response group to appeal directly to FEMA on behalf of those affected, and has had a high success rate.
However, FEMA will not disclose why it changes its mind on a case-by-case basis, making it almost impossible to understand the exact reasons it asked for the money in the first place.
http://news.sky.com/story/1365077/sandy-victims-forced-to-pay-back-recovery-funds