launching a dtsx package from a stored procedure

hi all,

I have this stored procedure:

BEGIN TRY

	DECLARE @execution_id bigint
	DECLARE @refID int
	
	EXEC [SSISDB].[catalog].[create_execution] 
		@package_name=N'myTextFileImport.dtsx',
		@folder_name=N'myFolder',
		@project_name=N'TextFileImport',
  		@use32bitruntime=False,
		@reference_id=5,
		@execution_id=@execution_id OUTPUT

	SELECT @execution_id
	DECLARE @var0 smallint = 1
	EXEC [SSISDB].[catalog].[set_execution_parameter_value] @execution_id,
		@object_type=50,
		@parameter_name=N'LOGGING_LEVEL',
		@parameter_value=@var0
	EXEC [SSISDB].[catalog].[start_execution] @execution_id

END TRY

When I run this in the SS Management Studio being logged with the domain account and Windows Authentication, the stored procedure runs OK and the package loads a text file to a table in a database.

However, when I call the same stored procedure from a web page through a dedicated database user I get this error message:

System.Data.SqlClient.SqlException (0x80131904): Error executing: Error loading: The operation cannot be started by an account that uses SQL Server Authentication. Start the operation with an account that uses Windows Authentication.

I have not seen an error message saying I cannot use a certain authentication before …

Any ideas what is happening here?

Thanks,

elsvieta