Allowed memory size of 1610612736 bytes exhausted (tried to allocate 4096 bytes)

After upgrading to the latest version 7.0.1 I have been getting a memory allocation issue.

Symfony\Component\ErrorHandler\Error\FatalError

Allowed memory size of 1610612736 bytes exhausted (tried to allocate 4096 bytes)

Here is the same code that is being used.

        $sitemap_count = 0;
        $sitemap = resolve('sitemap');

        Model::active()
              ->chunk(50000, function ( $objects ) use ( $sitemap, $sitemap_count ) {

                  $sitemap_count++;
                  $sitemap_filename = 'sitemap' . ($sitemap_count > 1 ? '-' . $sitemap_count : '');

                  foreach ($objects as $object) {
                      $sitemap->add($object->url);
                  }

                  $sitemap->store('xml', $sitemap_filename, $this->sitemap_path);
                  $sitemap->model->resetItems();
                  $sitemap->addSitemap(url('sitemaps/' . $sitemap_filename . '.xml.gz'), now());

              });

Memory constantly growing even though I am using the resetItems() method.

• sitemap (670MB)
• sitemap-2 (743MB)
• sitemap-3 (817MB)
• sitemap-4 (890MB)
• sitemap-5 (964MB)
• sitemap-6 (1037MB)
• sitemap-7 (1111MB)
• sitemap-8 (1184MB)
• sitemap-9 (1166MB)
• sitemap-9 (Boom!!!)

Here is a screenshot from the error log