* QIA sought approval for big Deutsche stake - sources
* Qatari officials haven't followed up - sources
* Sensitive issue amid merger talks with Commerzbank
FRANKFURT, April 9 (Reuters) - A plan by Qatar's sovereign wealth fund to make a significant investment in Deutsche Bank has stalled, according to two people with knowledge of the matter.
The fund Qatar Investment Authority (QIA) had approached financial regulators some months ago about a request for approval for a sizeable stake in Germany's largest lender, the people said.
But Qatari officials haven't yet provided the necessary documentation, which could derail QIA's investment plans.
It remains unclear whether QIA has lost interest or if it is taking its time.
Qatar initially expressed interest in the stake well before Deutsche Bank announced on March 17 that it was in talks to merge with Commerzbank. The issue is sensitive because the European Central Bank may ask Deutsche to raise fresh funds to approve any deal.
QIA, Deutsche Bank and Commerzbank declined to comment.
Rumours of the investment have been reported by various media outlets for months.
(Reporting by Hans Seidenstucker, John O'Donnell and Tom Sims; Additional reporting by Saeed Azhar and Davide Barbuscia in Dubai; Editing by)