Oracle 11g Standard Audit : unable to remove audit of SELECT

Hi,

I have a database on Oracle 11.2.0.4 on Oracle Linux. Audit trail parameters are set as follow:
audit_sys_operations = FALSE
audit_trail = DB_EXTENDED

I removed au the audit rules so these queries return nothing:
SELECT * FROM DBA_STMT_AUDIT_OPTS;
SELECT * FROM DBA_PRIV_AUDIT_OPTS;
SELECT * FROM DBA_OBJ_AUDIT_OPTS;
SELECT * FROM DBA_AUDIT_POLICIES;

One more information: there's a logon trigger.
With this setting, the instance is auditing all the SELECT and that's where I do not understand.
Any suggestions?
Thanks

Christophe